Positive photoresist used in a process for producing semiconductors must concurrently have different characteristics such as a property that an exposed portions becomes soluble in alkali by light irradiation, an ability of adhesion to silicon wafers, plasma-etching resistance, and transparency to used light. The positive photoresist is generally used as a solution containing a base component polymer, a light-activatable acid generator, and some sorts of additives for controlling the above characteristics. On the other hand, a wavelength of a light source of lithography used for manufacturing semiconductors has become shorter from year to year and the ArF excimer laser with a wavelength of 193 nm is promising as a next-generation light source. As a photoresist polymer used in the ArF excimer laser exposure system, various polymers having repeated units containing a lactone skeleton that exhibit high adhesion to substrates and an alicyclic hydrocarbon skeleton that exhibits high etching resistance have been proposed.
These polymers are ordinarily isolated by polymerizing a mixture of monomers, and subjecting the polymer solution to be allowed to precipitation procedure. There is, however, a problem that a required capability (sensitivity and others) isn't performed because of containing an impurity such as metal component in the resulting polymer when the polymer is used as a photoresist resin component. Particularly, when metal components such as sodium and iron are contained, an electrical characteristic of semiconductors declines. There is also a problem that a polymer is hard to be dissolved in a resist solvent because surface of the polymer particles become hard or the polymer particles are welded to each other.